Quick Answer:
Small bursts of air after nearby city line work are usually trapped air moving through the service line. Open the faucet fully to purge air and try hot-only and cold-only tests to narrow the source. If sputtering returns across multiple fixtures or floors, a plumber can trace the problem safely.
Why This Happens
When crews work on the municipal water main they often drain, depressurize, or refill sections of pipe. That process can let air into the service line to your house. Pressure changes push pockets of air into branch lines and fixtures; the air shows up as sputters, clicking noises, or short bursts of spray.
If the sputtering follows a heater refill or a brief outage, the water heater can trap and release air as it refills—see Air spurting after water heater refill for more on that pattern. Other causes include a loose or faulty check valve, venting issues, or partial obstructions that let air collect and then release.
Step-by-Step What to Do
1. Open the faucet fully to purge air
Turn the affected faucet to full open and let it run for a minute or two. A fully open valve lets trapped air pass quickly and helps clear the line.
2. Test hot-only vs cold-only
Run hot-only, then cold-only, and note which side spits. If air shows only on hot, the heater or its feed is likely involved. If only on cold, the issue is upstream of the heater.
3. Note timing: after outages or heater refills
- Record whether spitting started right after a city outage, a main shutoff, or after the water heater refilled. That timing points to whether the supply line or the heater introduced the air.
4. Check upstairs fixtures vs downstairs
Try the same test at sinks and showers on different floors. If upstairs behaves differently than downstairs, that helps locate the pocket of air. Repeating sputtering across multiple floors suggests the main supply or a common valve is the source.
5. What to observe while purging
- Does the sputter stop and stay stopped after a few minutes?
- Is there only a brief episode or a repeated on/off pattern?
- Does the water pressure dip when sputtering occurs?
What Not to Do
- Don’t keep cycling the main valve or dismantling cartridges. Doing so can make the problem worse or cause damage.
- Don’t open plumbing fixtures if you don’t know how to safely shut off the affected supply—avoid creating flooding risk.
- If air returns after purging or affects multiple floors, let a plumber inspect venting and supply components rather than attempting more invasive DIY fixes.
When to Call a Professional
Call a plumber if:
- The sputtering continues after you purge fixtures and test hot vs cold.
- Multiple fixtures and floors are affected, or the issue follows a brief loss of service.
- You notice pressure loss, banging noises, or irregular flow that comes back repeatedly.
A licensed plumber can trace the source with pressure gauges, shutoff isolation, and inspection of check valves, pressure-reducing valves, and the water heater. If air appears before water begins to flow at multiple fixtures, that’s often a sign of supply-side entrainment or a venting issue—see Air spits before water flows for that scenario.
Safety Notes
- Be careful when testing hot water—run cold-only first if you are unsure of the water heater temperature to avoid scalding.
- Avoid working on pressurized lines yourself. Shut off the main only if you know where it is and how to fully drain the system.
- If you suspect a leak or backflow, stop using the water and call a professional or your water utility.
Common Homeowner Questions
- Why did this start after the city fixed the main? Repairs and refills introduce air pockets; pressure changes push those pockets into service lines.
- Will it clear on its own? Often yes after a short purge, but repeated or multi-floor problems usually need a plumber.
- Could it damage my fixtures? Occasional air spurts are unlikely to damage fixtures, but ongoing pressure swings or debris can shorten valve and cartridge life.
For more related articles, see the Air Spitting From Faucets hub.